1. Field of the Invention
The present invention relates to a process for continuous mixing of two liquid components whose one component comprises a two-liquid curing type resin, more particularly, it relates to a process for mixing two liquid components especially at the time of starting of a mixing device.
2. Description of the Prior Art
As materials for molded articles such as synthetic resin films and synthetic resin sheets, synthetic resins of reactive curing type are often used, and as examples of the reactive curing type synthetic resins there are included polyimide resin, epoxy resin, urethane resin, phenol resin, unsaturated polyester resin and the like.
Such synthetic resins of the reactive curing type are known to be of two-liquid type and, when the two liquid components such as a resin component and a curing component are mixed together, the viscosity starts rising (curing starts) and continues rising until it is no longer moldable. The time for a synthetic resin to become unmoldable is called "pot life," and this pot life depends on the ambient temperature and the ratio of the two liquid components to be mixed together. In order to produce molded articles within this pot life, a continuous mixing device is positioned close to a molding device where two liquid components are mixed continuously before being supplied to the molding device.
A continuous mixing device for mixing two liquid components uniformly and rapidly without causing bubbles has been proposed in which one of two liquid components, for example, a resin is supplied continuously into a mixing container with stirring and the other liquid is poured into the mixing container by pushing open a needle forcibly provided to a check valve through pouring pressure, whereby the two liquid components are continuously mixed.
In this mixing device, a pouring pressure of the curing agent and a force by which the needle is forcibly provided to the check valve are balanced under normal operation so that the curing agent is poured into the mixing container at a predetermined rate. At the time of starting, however, as is shown by FIG. 5, the pouring pressure of the curing agent increases against the force by which the needle is forcibly provided to the check valve and reaches a given pressure to thus push open the needle, then decreases to a predetermined pressure during the normal operation while repeating an up-and-down quake.
At the time of initiating operation where the needle is pushed open, a greater amount of the curing agent than needed is inevitably introduced at a stroke into the mixing container, thus a ratio of the curing agent in the mixed solution being raised. With the mixed solution containing the curing agent at a high ratio, "pot life" of the mixed solution expires before discharge of it from the mixing container, which permits portions advanced in curing to remain in the mixing container. Those portions are cut into fine pieces by stirring blades and then discharged little by little from the mixing container. In cases where those give an adverse effect to molded articles, all of the molded articles lose commercial value.